The morphology of the plumular leaf was investigated for the 36 taxa (31 species and 5 subspecies) of Arisaema (Araceae) in Japan. Of the total, 22 taxa (18 species and 4 subspecies) were newly observed. Four morphological plumule patterns, i.e. without blade, with a simple and cordate blade, with a simple and hastate blade, and with a trifoliolate blade, were recognized. The patterns are considered in relation to the taxonomic treatment of Japanese Arisaema.